Trane UHMB060ACV3VA Service manual

Service Facts
© 2011 Trane All Rights Reserved NOTICE: Since the manufacturer has a policy of continuous product and product data
improvement, it reserves the right to change design and specifications with-
out notice.
PRODUCT SPECIFICATIONS 1
MODEL
TYPE
RATINGS 2
40%(low)heatInputBTUH
40%(low)heatCapacityBTUH(ICS) 36
100%(high)heatInputBTUH
100%(high)heatCapacityBTUH(ICS) 3
Temp.rise(Min.-Max.)°F.
AFUE
BLOWERDRIVE
Diameter-Width(In.)
No.Used
Speeds(No.)
CFMvs.in.w.g.
MotorHP
R.P.M.
Volts / Ph / Hz
COMBUSTIONFAN-Type
Drive- No.Speeds
MotorHP-RPM
Volts / Ph / Hz
FLA
FILTER — Furnished?
TypeRecommended
HiVel.(No.-Size-Thk.)
VENT — Size (in.)
HEATEXCHANGER
Type -Fired
-Unfired
Gauge (Fired)
ORIFICES — Main
Nat.Gas. Qty. — DrillSize
L.P.GasQty.—DrillSize5
GASVALVE
PILOT SAFETY DEVICE
Type
BURNERS — Type
Number
POWER CONN. — V / Ph / Hz 4
Ampacity (In Amps)
Max. Overcurrent Protection (Amps)
PIPE CONN. SIZE (IN.)
DIMENSIONS
Crated(In.)
WEIGHT
Shipping(Lbs.) / Net (Lbs)
*UHMB080ACV3VA
Upflow/ Horizontal
32,000
30,000
80,000
75,000
35-65
95.0
DIRECT
10x 8
1
Variable
SeeFanPerformanceTable
1/2
Variable
115/1/60
Centrifugal
Direct-Variable
1/50-5000
33-110/3/60-180
5.8
Yes
HighVelocity
1-17x25-1 in.
2Round
AluminizedSteel -TypeI
20
4—45
4—56
Modulating
HotSurfaceIgniter
MultiportInshot
4
115/1/60
8.7
15
1/2
HxWxD
41-3/4x19-1/2x30-1/2
168/156
IMPORTANT — This document contains a wiring diagram and service information. This is customer property and is to
remain with this unit. Please return to service information pack upon completion of work.
DISCONNECT POWER BEFORE SERVICING
WARNING
*UHMB060ACV3VA
Upflow/ Horizontal
24,000
23,000
60,000
57,000
35-65
95.0
DIRECT
10x 8
1
Variable
SeeFanPerformanceTable
1/2
Variable
115/1/60
Centrifugal
Direct-Variable
1/50-5000
33-110/3/60-180
5.8
Yes
HighVelocity
1-17x25-1 in.
2Round
AluminizedSteel -TypeI
20
3—45
3—56
Modulating
HotSurfaceIgniter
MultiportInshot
3
115/1/60
8.7
15
1/2
HxWxD
41-3/4x19-1/2x30-1/2
158/146
*UHMC100ACV4VA
Upflow/ Horizontal
40,000
38,000
100,000
95,000
35-65
95.0
DIRECT
10x 10
1
Variable
SeeFanPerformanceTable
1
Variable
115/1/60
Centrifugal
Direct-Variable
1/50-5000
33-110/3/60-180
7.8
Yes
HighVelocity
1-20x25-1 in.
3Round
AluminizedSteel -TypeI
20
5—45
5—56
Modulating
HotSurfaceIgniter
MultiportInshot
5
115/1/60
11.2
20
1/2
HxWxD
41-3/4x23x30-1/2
197/185
*UHMD120ACV5VA
Upflow/ Horizontal
54,000
52,000
120,000
114,000
40-70
95.0
DIRECT
10x 10
1
Variable
SeeFanPerformanceTable
1
Variable
115/1/60
Centrifugal
Direct-Variable
1/50-5000
33-110/3/60-180
10.2
Yes
HighVelocity
1-24x25-1 in.
3Round
AluminizedSteel -TypeI
20
6—45
6—56
Modulating
HotSurfaceIgniter
MultiportInshot
6
115/1/60
14.2
20
1/2
HxWxD
41-3/4x26-1/2x30-1/2
206/193
1Central Furnace heating designs are certified to ANSI Z21.47 / CSA 2.3.
2For U.S. applications, above input ratings (BTUH) are up to 2,000 feet, derate 4% per 1,000 feet for elevations above 2,000 feet above sea level.
For Canadian applications, above input ratings (BTUH) are up to 4,500 feet, derate 4% per 1,000 feet for elevations above 4,500 feet above sea level.
3Based on U.S. government standard tests.
4The above wiring specifications are in accordance with National Electrical Code; however, installations must comply with local codes.
5Furnace ships in natural gas configuration. The LP conversion kit used with the modulating furnace is BAYLPSS220B or BAYLPKT220B.
645% (low) heat for *UHM1D120ACV5VA.
Upflow/ Horizontal Left and Downflow/ Horizontal Right,
Gas-Fired, Direct/Non-Direct Vent, Variable Speed,
Modulating, Condensing, Communicating Furnaces
*UHMB060ACV3VA
*UHMB080ACV3VA
*UHMC100ACV4VA
*UHMD120ACV5VA
*DHMB060BCV3VA
*DHMB080ACV3VA
*DHMC100ACV4VA
*DHMD120BCV5VA
* First letter may be “A” or “T" This furnace can be configured
for Communicating or 24 VAC
modes.
*UHM-DHM-SF-1H

2UHM-DHM-SF-1H
Service Facts
PRODUCT SPECIFICATIONS 1
MODEL
TYPE
RATINGS 2
40%(low)heatInputBTUH
40%(low)heatCapacityBTUH(ICS) 3
100%(high)heatInputBTUH
100%(high)heatCapacityBTUH(ICS) 3
Temp.rise(Min.-Max.)°F.
AFUE
BLOWERDRIVE
Diameter-Width(In.)
No.Used
Speeds(No.)
CFMvs.in.w.g.
MotorHP
R.P.M.
Volts / Ph / Hz
COMBUSTIONFAN-Type
Drive- No.Speeds
MotorHP-RPM
Volts / Ph / Hz
FLA
FILTER — Furnished?
TypeRecommended
HiVel.(No.-Size-Thk.)
VENT — Size (in.)
HEATEXCHANGER
Type -Fired
-Unfired
Gauge (Fired)
ORIFICES — Main
Nat.Gas. Qty. — DrillSize
L.P.GasQty.—DrillSize 5
GASVALVE
PILOT SAFETY DEVICE
Type
BURNERS — Type
Number
POWER CONN. — V / Ph / Hz 4
Ampacity (In Amps)
Max. Overcurrent Protection (Amps)
PIPE CONN. SIZE (IN.)
DIMENSIONS
Crated(In.)
WEIGHT
Shipping(Lbs.) / Net (Lbs)
*DHMC080ACV3VA
Downflow / Horizontal
32,000
30,000
80,000
74,000
35-65
95.0
DIRECT
10x 8
1
Variable
SeeFanPerformanceTable
1/2
Variable
115/1/60
Centrifugal
Direct-Variable
1/50-5000
33-110/3/60-180
5.8
Yes
HighVelocity
2-14x20-1 in.
2Round
AluminizedSteel -Type I
20
4—45
4—56
Modulating
HotSurfaceIgniter
MultiportInshot
4
115/1/60
8.7
15
1/2
HxWxD
41-3/4x19-1/2x30-1/2
168/158
*DHMD120BCV5VA
Downflow / Horizontal
48,000
45,600
120,000
114,000
40-70
95.0
DIRECT
10x 10
1
Variable
SeeFanPerformanceTable
1
Variable
115/1/60
Centrifugal
Direct-Variable
1/50-5000
33-110/3/60-180
10.2
Yes
HighVelocity
2-16x20-1 in.
3Round
AluminizedSteel -Type I
20
6—45
6—56
Modulating
HotSurfaceIgniter
MultiportInshot
6
115/1/60
14.2
20
1/2
HxWxD
41-3/4x26-1/2x30-1/2
206/196
*DHMC100ACV4VA
Downflow / Horizontal
40,000
38,000
100,000
95,000
35-65
95.0
DIRECT
10x 10
1
Variable
SeeFanPerformanceTable
3/4
Variable
115/1/60
Centrifugal
Direct-Variable
1/50-5000
33-110/3/60-180
7.8
Yes
HighVelocity
2-16x20-1 in.
3Round
AluminizedSteel -Type I
20
5—45
5—56
Modulating
HotSurfaceIgniter
MultiportInshot
5
115/1/60
11.2
20
1/2
HxWxD
41-3/4x23x30-1/2
185/175
*DHMB060BCV3VA
Downflow / Horizontal
24,000
22,800
60,000
57,000
30-60
95.0
DIRECT
10x 8
1
Variable
SeeFanPerformanceTable
1/2
Variable
115/1/60
Centrifugal
Direct-Variable
1/50-5000
33-110/3/60-180
5.8
Yes
HighVelocity
2-14x20-1 in.
2Round
AluminizedSteel -Type I
20
3—45
3—56
Modulating
HotSurfaceIgniter
MultiportInshot
3
115/1/60
8.7
15
1/2
HxWxD
41-3/4x19-1/2x30-1/2
160/146
1Central Furnace heating designs are certified to ANSI Z21.47 / CSA 2.3.
2For U.S. applications, above input ratings (BTUH) are up to 2,000 feet, derate 4% per 1,000 feet for elevations above 2,000 feet above sea level.
For Canadian applications, above input ratings (BTUH) are up to 4,500 feet, derate 4% per 1,000 feet for elevations above 4,500 feet above sea level.
3Based on U.S. government standard tests.
4The above wiring specifications are in accordance with National Electrical Code; however, installations must comply with local codes.
5Furnace ships in natural gas configuration. The LP conversions kit used with the modulating furnace is BAYLPSS220B or BAYLPKT220B.
NOTE:
This furnace can be configured for Communicating or
24 VAC modes. Using fully Communicating or 24 VAC
modes, the furnace can support single or multi stage
heat pump, AC, or heating only applications. Com-
bined with a communicating Comfort Control only, the
furnace will support a single stage 24 VAC cooling
outdoor unit only.
NOTE:
CONTINUOUS fan mode during COOLING operation
may not be appropriate in humid climates. If the
indoor air exceeds 60% relative humidity or simply
feels uncomfortably humid, it is recommended that the
fan only be used in the AUTO mode.
A communicating comfort control will disable a
continuous fan call if the relative humidity exceeds the
set point. See the Troubleshooting Information section
of the Communicating Comfort Control Installer’s
Guide for details.

UHM-DHM-SF-1H 3
Service Facts
SAFETY SECTION
▲
WARNING
!
FIRE OR EXPLOSION HAZARD
Failure to follow the safety warnings exactly could re-
sult in serious injury, death or property damage.
Never test for gas leaks with an open flame. Use a com-
mercially available soap solution made specifically for
the detection of leaks to check all connections. A fire
or explosion may result causing property damage, per-
sonal injury, or loss of life.
▲
WARNING
!
FIRE OR EXPLOSION HAZARD
Failure to follow the safety warnings exactly could re-
sult in serious injury, death or property damage.
Improper servicing could result in dangerous opera-
tion, serious injury, death, or property damage.
▲
WARNING
!
BODILY INJURY CAN RESULT FROM HIGH VOLTAGE
ELECTRICAL COMPONENTS, FAST MOVING FANS,
AND COMBUSTIBLE GAS. FOR PROTECTION FROM
THESE INHERENT HAZARDS DURING INSTALLATION
AND SERVICING, THE ELECTRICAL SUPPLY MUST BE
DISCONNECTED AND THE MAIN GAS VALVE MUST BE
TURNED OFF. IF OPERATING CHECKS MUST BE
PERFORMED WITH THE UNIT OPERATING, IT IS THE
TECHNICIAN’S RESPONSIBILITY TO RECOGNIZE
THESE HAZARDS AND PROCEED SAFELY.
▲
WARNING
!
Should overheating occur, or the gas supply fail to
shut off, shut off the Gas Valve to the unit before shut-
ting off the electrical supply.
Failure to follow this warning could result in property
damage, personal injury, or death.
▲
CAUTION
!
The integrated furnace control is polarity sensitive. The
hot leg of the 115 VAC power must be connected to the
BLACK field lead
NOTE:
CONTINUOUS fan mode during COOLING operation
may not be appropriate in humid climates. If the
indoor air exceeds 60% relative humidity or simply
feels uncomfortably humid, it is recommended that the
fan only be used in the AUTO mode.
A communicating comfort control will disable a
continuous fan call if the relative humidity exceeds the
set point. See the Troubleshooting Information section
of the Communicating Comfort Control Installer’s
Guide for details.
▲
WARNING
!
The cabinet must have an uninterrupted or unbroken
ground according to National Electrical Code, ANSI/
NFPA 70 - “latest edition” and Canadian Electrical
Code, CSA C22.1 or local codes to minimize personal
injury if an electrical fault should occur.
Failure to follow this warning could result in an electri-
cal shock, fire, injury, or death.
▲
WARNING
!
CARBON MONOXIDE POISONING HAZARD
Failure to follow the installation instructions for the
venting system being placed into operation could re-
sult in carbon monoxide poisoning or death.
CARBON MONOXIDE POISONING HAZARD
Failure to follow the steps outlined below for each
appliance connected to the venting system being
placed into operation could result in carbon monoxide
poisoning or death.
The following steps shall be followed for each appliance
connected to the venting system being placed into
operation, while all other appliances connected to the
venting system are not in operation:
1. Seal any unused openings in the venting system.
2. Inspect the venting system for proper size and
horizontal pitch, as required in the National Fuel Gas
Code, ANSI Z223.1/NFPA 54 or the CAN/CGA B149
Installation Codes and these instructions. Determine
that there is no blockage or restriction, leakage,
corrosion and other deficiencies which could cause an
unsafe condition.
3. As far as practical, close all building doors and
windows and all doors between the space in which the
appliance(s) connected to the venting system are
located and other deficiencies which could cause an
unsafe condition.
4. Close fireplace dampers.
5. Turn on clothes dryers and any appliance not
connected to the venting system. Turn on any exhaust
fans, such as range hoods and bathroom exhausts, so
they are operating at maximum speed. Do not operate
a summer exhaust fan.
6. Follow the lighting instructions. Place the appliance
being inspected into operation. Adjust the thermostat
so appliance is operating continuously.
7. If improper venting is observed during any of the above
tests, the venting system must be corrected in
accordance with the National Fuel Gas Code,
ANSI Z221.1/NFPA 54 and/or CAN/CGA B149
Installation Codes.
8. After it has been determined that each appliance
connected to the venting system properly vents where
tested as outlined above, return doors, windows,
exhaust fans, fireplace dampers and any other gas-fired
burning appliance to their previous conditions of use.
▲
WARNING
!

4UHM-DHM-SF-1H
Service Facts
Heat Exchanger (Cold Header)
Burner Box
H-Fitting
Pressure
Switch
PS-1
Tee
Tee
Tee
Pressure Switch
PS-3
Pressure
Switch
PS-2
Negative
Control
Pressure
Post
Positive Control
Pressure Post
Modulating
Gas Valve
Orifice in H fitting must
be pointing away from PS1
FURNACE COMPONENTS
To Pressure
Switch PS-1
! Important !
Brass orifices located in these two legs.
H-Fitting must be installed in this orientation.
VACUUM HOSE ROUTING
▲
WARNING
!
FIRE - EXPLOSION HAZARD
DO NOT RUN FLEXIBLE GAS LINE THROUGH THE
FURNACE CABINET WALL OR WITHIN THE FURNACE
CABINET. FAILURE TO FOLLOW THIS WARNING
COULD RESULT IN PROPERTY DAMAGE, SERIOUS
PERSONAL INJURY, OR DEATH.
1
2
3

UHM-DHM-SF-1H 5
Service Facts
USER INTERFACE DISPLAY
USER INTERFACE
ENTER
Push left & right
to scroll through
menu options
Push up & down
to scroll through
setup menu
Push ENTER
to make selection
Viewing Window
User Interface pictured above adjusts variable speed airflow options and other unit settings
Service procedure to access the User Inter-
face for the Modulating Furnace
This procedure must only be performed by trained
service personnel.
▲
WARNING
!
ELECTRICAL SHOCK HAZARD
DO NOT BYPASS THE DOOR SWITCH BY ANY PER-
MANENT MEANS.
FAILURE TO FOLLOW WARNING COULD RESULT IN
SERIOUS PERSONAL INJURY OR DEATH.
▲
WARNING
!
ELECTRICAL SHOCK HAZARD
DO NOT TOUCH ANY COMPONENTS OTHER THAN
THE DISPLAY ASSEMBLY AND THE DOOR SWITCH
DURING THIS PROCEDURE.
FAILURE TO FOLLOW WARNING COULD RESULT IN
SERIOUS PERSONAL INJURY OR DEATH.
1. Remove Blower Door panel by turning the two
door latches ¼ turn.
2. Lower door panel and remove from service access
area.
3. Using one hand, depress the door switch (there
must be power to the control system for the Dis-
play Assembly to function) and keep the door
switch depressed during programming.
4. Using the other hand move through the Display
Assembly menu using the arrow buttons.
5. The User Interface menu on pages 5 and 6 is a
guide to the menu options.
6. When programming is complete release door
switch and replace the Blower Door.
4

6UHM-DHM-SF-1H
Service Facts
USER INTERFACE MENU
Power Up
== WAIT ==
A/TCONT900 Variable Speed
Standy Screen System Status Setup Options [ ] = Current Setting
MODEL NUMBER CMFRT CNT MODE
SERIAL NUMBER COMM [COMM] 24VAC
* Unit specific
COOLING CFM 2COOLING CFM A/TUHMB060 3T [3T] 1.5T 2T 2.5T
* A/TUHMB080 3T [3T] 3.5T 2T 2.5T
A/TUHMC100 4T [4T] 2.5T 3T 3.5T
CFM PER TON CFM PER TON A/TUHMD120 5T [5T] 3.5T 4T
400 [ 400 ] 430 450 290 310 330 350 370 A/TDHMB060 3T [3T] 1.5T 2T 2.5T
A/TDHMB080 3T [3T] 3.5T 2T 2.5T
HEAT CFM HEAT CFM A/TDHMC100 4T [4T] 2.5T 3T 3.5T
** A/TDHMD120 5T [5T] 3.5T 4T
HT OFF DELAY HEAT OFF DLY ** Unit specific
100s [100s] 140s 180s 60s A/TUHMB060 960 [960] 1080 830 900
A/TUHMB080 1400 [1400] 1610 1120 1260
FACTORY DEFLTS FACTORY DEFLTS A/TUHMC100 1620 [1620] 1790 1460 1540
NO [NO] YES A/TUHMD120 1890 [1890] 2000 1700 1790
A/TDHMB060 1040 [1040] 1160 900 950
EXIT EXIT A/TDHMB080 1400 [1400] 1610 1300 1350
NO [NO] YES A/TDHMC100 1650 [1650] 1700 1500 1600
A/TDHMD120 1850 [1850] 2040 1660 1760
Information Menu Information Options
MODEL NUMBER MODEL
A/TUHM####
SERIAL NUMBER SERIAL
#####
SW REV NUMBER SW REV NUMBER
#####
SYSTEM STATUS SYSTEM STATUS
OFF
REQUESTED CFM REQUESTED CFM
0 CFM
LAST 4 FAULTS LAST 4 FAULTS
NO ALERTS
INDOOR ALERTS INDOOR ALERTS
NO ALERTS
UNIT TEST UNIT TEST UNIT TEST UNIT TEST
SIMPLE GAS VAL SETUP
TEMP SENSOR TEMP SENSOR
SNSR1 [SNSR1] SNSR2 DLT2-1
UNIT TEST SIMPLE GAS VAL SETUP
MOTOR RPM MOTOR RPM NO [NO] YES MIN [MIN] MAX
0 RPM
INDUCER RPM INDUCER RPM
0 RPM ARE YOU SURE ARE YOU SURE
NO [NO] YES NO [NO] YES
RESET LST FAULT RESET LST FAULT
NO [NO] YES
PART LIST PART LIST
CNT*****
PM SERIAL NUM PM SERIAL NUM
#####
CNTNGNCY MODE CNTNGNCY MODE OR CNTNGNCY MODE 1
NOT AVAILABLE (with data line connected and active) NO [YES] YES (no data line connected)
EXIT EXIT
NO [NO] YES CNTNGNCY MODE <STAGE> CNTNGNCY MODE <STAGE>
STAGE [OFF] OFF 1 2
DUTY CYCLE [10] 10 20 30 40 50
START [NO] NO YES
NOTES: EXIT [NO] NO YES
1This menu will only display at comfort control mode when A/TCONT900 is NOT connected
ARE YOU SURE [NO] NO YES
ENTER
2Shown only when Communicating Outdoor Unit is not detected
ENTER
ENTER
ENTER

UHM-DHM-SF-1H 7
Service Facts
24V Variable Speed
System Status Setup Options [ ] = Current Setting
CMFRT CNT MODE
COMM [24VAC] 24VAC
* Unit specific
A/TUHMB060 3T [3T] 1.5T 2T 2.5T
COOLING CFM 2COOLING CFM A/TUHMB080 3T [3T] 3.5T 2T 2.5T
* A/TUHMC100 4T [4T] 2.5T 3T 3.5T
A/TUHMD120 5T [5T] 3.5T 4T
CFM PER TON CFM PER TON A/TDHMB060 3T [3T] 1.5T 2T 2.5T
400 [ 400 ] 430 450 290 310 330 350 370 A/TDHMB080 3T [3T] 3.5T 2T 2.5T
A/TDHMC100 4T [4T] 2.5T 3T 3.5T
CLG STAGES CLG STAGES A/TDHMD120 5T [5T] 3.5T 4T
1 STG [1 STG] 2 STGS
** Unit specific
CLG 1ST STG CFM 3CLG 1ST STG CFM 2A/TUHMB060 960 [960] 1080 830 900
50% [50%] 55% 65% 80% A/TUHMB080 1400 [1400] 1610 1120 1260
A/TUHMC100 1620 [1620] 1790 1460 1540
CONT FAN CFM CONT FAN CFM A/TUHMD120 1890 [1890] 2000 1700 1790
50% [50%] 75% 100% 25% A/TDHMB060 1040 [1040] 1160 900 950
A/TDHMB080 1400 [1400] 1610 1300 1350
FAN PRERUN DLY FAN PRERUN DLY A/TDHMC100 1650 [1650] 1700 1500 1600
NONE [NONE] 1m@50% A/TDHMD120 1850 [1850] 2040 1660 1760
FAN SHRTRUN DLY FAN SHRTRUN DLY
NONE [NONE] 4m@80% 7.5m@80%
FAN OFF DLY FAN OFF DLY
1.5m@100% [1.5m@100%] NONE 1m@50% 2m@50% 3m@50%
HEAT CFM HEAT CFM
**
HT OFF DELAY HT OFF DELAY
100s [100s] 140 180 60
W1 W2 STG DLY W1 W2 STG DLY
00m [00m] 5m 10m 15m
FACTORY DEFLTS FACTORY DEFLTS
NO [NO] YES
EXIT EXIT
NO [NO] YES
NOTES:
3This menu will only display when 2 STGS is chosen in previous menu.
2Shown only when Communicating Outdoor Unit is not detected

8UHM-DHM-SF-1H
Service Facts
NOTE: Y1 is output to non-communicating outdoor
unit
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Communicating
Comfort Control
SEQUENCE OF OPERATION
SEQUENCE OF OPERATION – COMMUNICATING
MODE
1. This furnace is fully modulating between 40% and
100% of capacity in 1% increments. The furnace
always lights at approximately 65% and will
modulate up or down; depending on the commu-
nicating comfort control demand. Requested
capacity can be seen in the “STATUS” section of
the User Interface menu.
Note:
Pressure Switch 1 closes at approximately 40%
of capacity.
Pressure Switch 2 closes at approximately 65%
of capacity.
Pressure Switch 3 closes at approximately 95%
of capacity.
2. The communicating comfort control signals the
furnace IFC for heat.
3. The IFC then checks all safeties, thermostats, and
pressure switches PS1, PS2, and PS3.
4. The IFC signals the variable speed inducer drive
to start the vent motor at the speed needed to
close pressure switches PS1 and PS2.
5. PS1 and PS2 close.
6. The IFC receives a 24 VAC signal from PS1 and
PS2 when they close. This verifies the vent
motor is moving the correct amount of combus-
tion air through the furnace and the vent system.
7. IFC starts the hot surface ignitor learning routine
warm-up time cycle.
8. IFC turns on the gas valve. Trial time for ignition
is 5 seconds.
Note:
The furnace lights at approximately 65% of capacity.
9. The IFC verifies ignition by the flame current
sensing method. If a flame is not detected, the
IFC will cycle the furnace three times to try and
verify a flame. If no flame is detected, the IFC
will lockout for one hour.
The IFC will send an alert code to the communi-
cating comfort control and User Interface. The
Red alert LED two times repeatedly.
10. If a flame is detected, the IFC will start the heat
exchanger warm-up time delay for the indoor
blower.
11. “IGNITION” will now be displayed in the “STA-
TUS” section of the User Interface menu.
12. After 45 seconds, the IFC signals the indoor
blower motor to run at the programmed ignition
sequence speed.
13. Depending on the communicating comfort control
demand, the IFC will then signal the variable
speed inducer motor drive board and the indoor
blower motor to ramp up or down.
5

UHM-DHM-SF-1H 9
Service Facts
14. With a heat demand less than 65% from the
communicating comfort control, the IFC signals
the variable speed inducer motor drive board to
ramp down to that corresponding demand speed.
The reduction of the vent motor speed in steps
allows the gas flow through the gas valve to also
be reduced in steps, decreasing the chance of
burner flame out. The minimum capacity change
is 1%.
15. The minimum capacity of all furnaces is 40%,
with the exception of the *UHMD120. The mini-
mum capacity for this furnace is 45%.
16. The communicating comfort control will continue
to call for the requested capacity demand until
the indoor temperature is back at the set point
OR,
17. If the communicating comfort control does not
detect that the indoor temperature is moving
back towards its set point or the indoor tempera-
ture is still moving away from the set point, it
will signal the IFC to go to a higher capacity of
heat.
18. The IFC then signals the variable speed inducer
drive to ramp up the vent motor in steps. As the
vent motor speed increases the amount of gas
coming through the gas valve will increase. The
IFC will also increase the indoor blower motor
speed.
19. The communicating comfort control will continue
to monitor the indoor temperature and send
signals to the IFC to modulate the heating capac-
ity or turn off to maintain the homeowner's set
point.
20. Once the communicating comfort control senses
that the heating requirements have been satis-
fied, the gas valve will be de-energized and gas
flow will cease. The variable speed vent motor
will de-energize approximately after a 5 second
post purge. All pressure switches will open and
the indoor blower motor will then run the heat
off delay that is selected in the User Interface
menu.
Indoor Blower motor operation thermostat fan
switch “ON” (Communicating Mode)
The communicating comfort control signals a contin-
uous fan call. The factory setting is 50% of the cool-
ing cfm selected but can be adjusted from 25% - 100%
through the Installer Setup menu on the communi-
cating comfort control. If the outdoor unit is a 2
stage system, the factory setting is 50% of the 2nd
stage cooling cfm. If the outdoor unit is a 24 volt
single stage cooling system, the factory setting is 50%
of the cooling cfm.
NOTE: If the actual relative humidity (RH) is at or
below the set-point, the fan will run until the contin-
uous fan call is removed or the actual RH exceeds the
set-point. If the actual RH is above the set-point, the
fan will not turn on.
See the communicating comfort control Installer's
Guide for additional information.
SEQUENCE OF OPERATION – 24VAC Mode
1. This furnace modulates between 40% and 100% of
capacity, in 3% increments, every 1 minute. The
furnace always lights at approximately 65% and
will modulate up or down; depending on the
24VAC thermostat signal. Requested capacity can
be seen in the “STATUS” section of the User
Interface menu.
Note:
Pressure Switch 1 closes at approximately 40%
of capacity.
Pressure Switch 2 closes at approximately 65%
of capacity.
Pressure Switch 3 closes at approximately 95%
of capacity.
Thermostat call for W1 (2 stage heating thermo-
stat)
2. R and W1 contacts close signaling the control
board (IFC) to run its self- check routine. After
the control has verified that all safeties are closed
and PS1, PS2, and PS3 pressure switch contacts
are open, the IFC signals the variable speed
inducer drive to start the vent motor at the speed
needed to close pressure switches PS1 and PS2.
Note:
The furnace lights at approximately 65% of capacity.
3. PS1 and PS2 close.
4. The IFC receives a 24 VAC signal from PS1 and
PS2 when they close. This verifies the vent
motor is moving the correct amount of combus-
tion air through the furnace and the vent system.
5. IFC starts the hot surface ignitor learning routine
warm-up time cycle.
6. IFC turns on the gas valve. Trial time for ignition
is 5 seconds.
7. The IFC verifies ignition by the flame current
sensing method. If a flame is not detected, the
IFC will cycle the furnace three times to try and
verify a flame. If no flame is detected, the IFC
will lockout for one hour. The IFC will send an
alert code to the communicating comfort control
and User Interface as well as flash its Red alert
LED two times repeatedly.
8. If a flame is detected, the IFC will start the heat
exchanger warm-up time delay for the indoor
blower.

10 UHM-DHM-SF-1H
Service Facts
9. “IGNITION” will now be displayed in the “STA-
TUS” section of the User Interface menu.
10. After 45 seconds, the IFC signals the indoor
blower motor to run at the programmed ignition
sequence speed.
11. The IFC then signals the variable speed inducer
motor drive board to ramp down to the corre-
sponding speed to keep PS1 closed. The reduction
of the vent motor speed in steps allows the gas
flow through the gas valve to also be reduced in
steps, decreasing the chance of burner flame out.
The W1 heating capacity is 40%. The IFC will
also decrease the indoor blower motor speed.
Thermostat call for W2 after W1
12. R and W2 thermostat contacts close signaling a
call for W2 heat. The IFC then signals the vari-
able speed inducer drive to ramp up the vent
motor allowing flow through the gas valve to also
be increased in 3% steps.
13. If the call for W2 remains, this 3% increase will
be repeated every 1 minute until the capacity
requested is 100%. The IFC will also increase the
indoor blower motor speed in appropriate steps.
W2 satisfied, W1 still called for
14. R and W2 thermostat contacts open signaling
that W2 heating requirements have been satis-
fied. The IFC will signal the variable speed vent
motor to slow down to its learned W1 speed. The
gas valve will reduce the gas flow to 40% capacity
and the indoor blower motor speed will be re-
duced.
W1 satisfied
15. R and W1 thermostat contacts open signaling
that W1 heating requirements have been satis-
fied. The gas valve will be de-energized and gas
flow will cease. The variable speed vent motor
will de-energize approximately after a 5 second
post purge.
The indoor blower motor will be de-energized
after the fan off delay period has ended. (The
indoor blower heat fan off delay is field selectable
and can be adjusted using the User Interface
menu. It is factory set at 100 seconds but can be
set to 60, 140, or 180 seconds)
Thermostat call for heat (1 stage heating ther-
mostat)
16. W1 and W2 must be jumpered at the IFC. R and
W1 contacts close signaling the control board
(IFC) to run its self- check routine. After the
control has verified that all safeties are closed
and PS1, PS2, and PS3 pressure switch contacts
are open, the IFC signals the variable speed
inducer drive to start the vent motor at the speed
needed to close pressure switches PS1 and PS2.
Note:
The furnace lights at approximately 65% of capacity.
17. PS1 and PS2 close.
18. The IFC receives a 24 VAC signal from PS1 and
PS2 when they close. This verifies the vent
motor is moving the correct amount of combus-
tion air through the furnace and the vent system.
19. IFC starts the hot surface ignitor learning
routine warm-up time cycle.
20. IFC turns on the gas valve. Trial time for igni-
tion is 5 seconds.
21. The IFC verifies ignition by the flame current
sensing method. If a flame is not detected, the
IFC will cycle the furnace three times to try and
verify a flame. If no flame is detected, the IFC
will lockout for one hour. The IFC will send an
alert code to the communicating comfort control
and User Interface as well as flash its Red alert
LED two times repeatedly.
22. If a flame is detected, the IFC will start the heat
exchanger warm-up time delay for the indoor
blower.
23. “IGNITION” will now be displayed in the “STA-
TUS” section of the User Interface menu.
24. After 45 seconds, the IFC signals the indoor
blower motor to run at the programmed ignition
sequence speed.
25. Every 1 minute, the IFC will signal the vent
motor to ramp up. The increase of the vent
motor speed allows the gas flow through the gas
valve to also be increased in 3% steps. This 3%
increase will be repeated every 1 minute until
the capacity requested is 100%. Pressure switch 3
closes at approximately 95% of capacity.
26. The IFC will also increase the indoor blower
motor speed in appropriate steps. (The inter-
stage delay is field selectable and can be adjusted
through the User interface menu.
It is factory set at 0 minutes but can be adjusted
to 5, 10, or 15 minutes.) This option can help
optimize the furnace to try to satisfy the heating
requirement during low heating load conditions.
Indoor Blower motor operation thermostat fan
switch “CONTINUOUS” (24V Mode)
R and G comfort control contacts close signaling a
continuous fan call. The continuous fan cfm is field
selectable and can be adjusted through the User
Interface menu. The factory setting is 50% of the
cooling cfm selected but can be set at 25%, 50%, 75%,
or 100%. If the system has a 2 stage outdoor unit, the
setting is 50% of the 2nd stage cooling cfm.

UHM-DHM-SF-1H 11
Service Facts
B) GAS VALVE SETUP (MANIFOLD PRESSURE AD-
JUSTMENT)
NOTE: To obtain an accurate manifold pressure
measurement ,the manifold pressure must be refer-
enced to the burner box, since the burner box pres-
sure tap equalizes the gas valve pressure regulator.
To do so, install a tee and section of tube (field
supplied) in the tubing between the tee coming from
the burner box tube and the gas valve manifold
pressure measurement fitting. This tube and tee is
in addition to the tube attached to the gas valve
pressure tap on the outlet side of the gas valve. See
Figure 7.
NOTE: In order to properly set the manifold gas
pressure, the incoming line gas pressure should be
tested with the unit off and again with the unit
operating at the high heat setting to ensure adequate
fuel supply to the furnace. The incoming gas pres-
sure should be 5" W.C. minimum and 13.8" W.C.
maximum for natural gas.
1) Before Setting Manifold Gas Pressure
Setting the manifold gas pressures is critical for the
correct operation of this furnace.
Before entering the Gas Valve Setup mode:
a. Turn comfort control system switch to the OFF
position and fan switch to the AUTO position.
b. Prime the furnace condensate trap.
Any call for heat or fan by the comfort control will abort
or cancel the Gas Valve Setup mode. The unit will
stay in Gas Valve Setup mode for a maximum of 20
minutes.
c. Connect dual port manometer & field tubing per
Figure 6.
Note: MIN = 40% (low) heat, MAX = 100% (high) heat
Setting Manifold Gas Pressure
2) Setting “MIN” manifold gas pressure
To enter the Gas Valve Setup mode:
a. Scroll down on the user interface to Unit Test.
b. Scroll to the right and select “Gas Val Setup”.
c. Push the Enter button.
d. Select “MIN” and push the Enter button.
e. When asked “Are You Sure”, select Yes, and push
the Enter button.
f. The furnace will now begin the ignition sequence.
g. If pressure switch 1 & 2 learning routines have not
been performed; after successful ignition, the
inducer will go through this operation. (see Inducer
Learning Routine section).
UNIT TEST MODE
A) SIMPLE
Note:
Stage 1 = 40% (low) heat, Stage 2 = 100% (high) heat
A qualified technician can cycle the Variable
Speed Indoor Blower and the Modulating Gas
Furnace through its operation at the User
Interface.
•The unit test cycle is entered at the user
interface.
•The test cycle can only be entered when the
comfort control has no demand and the furnace
IFC is not reporting a fault. Turn the com-
fort control to the Off position and turn
the fan control to Auto. This will ensure
the unit test cycle will not be interrupted.
•Scroll down using the 6button at the user
interface until the display reads:
•UNIT TEST. Press the Enter button.
•UNIT TEST and 3NO (NO) 4will now be
displayed. Use the 3or 4arrow button to
change the NO to a YES and then press ENTER.
•ARE YOU SURE and NO (NO) will now be
displayed. Use the 3or 4arrow button to
change the NO to a YES and then press ENTER.
• UNIT TEST and Y1 ON FAN ON will now be dis-
played.The variable speed indoor blower will then
be turned on by the IFC for 10 seconds and then
off.
•Furnace will then transition to the ignition se-
quence. STAGE OFF will now be displayed.
After a 45 second heat fan on delay, Stage 1 will
be displayed and 40% (low) heat inducer speed
will be energized for 10 seconds.
•Stage 2 will be displayed and 100% (high) heat in-
ducer speed will be energized for 10 seconds.
•The control transitions to off.
•The Model and Serial Number will be displayed.
•The variable speed indoor blower will now
operate for the heat exchanger cool down cycle
andthen shut off at the end of the cycle.
•The comfort control can now be returned to the
homeowner’s desired settings.

12 UHM-DHM-SF-1H
Service Facts
CORRECT METHOD OF CHECKING DIRECT VENT MANIFOLD PRESSURE
WITH BURNER BOX REFERENCED
Manifold
Pressure
Measurement
Fitting
Field Supplied
Connects to
Burner Box
Pressure Hose
A Field Supplied barb fitting must be used
on the gas valve to attach the hose
Gas Valve
On/ Off
Toggle
Switch
High Heat
Manifold
Pressure
(Adjustment
under cover)
Inlet Pressure
Measurement Fitting
7
Negative Control
Pressure Post Positive Control
Pressure Post
Low Heat Manifold
Pressure
(Adjustment under
cover)
Manifold
Pressure
Measurement
Fitting
Flow
TABLE 1
Furnace Input rate
(KBTU/hr) FINAL LP MANIFOLD PRESSURE SETTINGS (inches w.c
.)
40% 65% 100%
60 2.1 ± 0.5 Not Adjustable 10.0 ± 0.5
80 2.1 ± 0.5 Not Adjustable 10.0 ± 0.5
100 2.1 ± 0.5 Not Adjustable 10.0 ± 0.5
Downflow 120 2.1 ± 0.5 Not Adjustable 10.0 ± 0.5
Upflow 120 2.9 ± 0.5 Not Adjustable 10.0 ± 0.5
For upflow 120KBTU/hr model, 1st stage is 45%
Manifold pressures apply for Propane applications ONLY
Furnace Input rate
(KBTU/hr) FINAL NG MANIFOLD PRESSURE SETTINGS (inches w.c
.)
40% 65% 100%
60 0.7 + 0.2 / - 0.0 Not Adjustable 3.5 ± 0.2
80 0.7 + 0.2 / - 0.0 Not Adjustable 3.5 ± 0.2
100 0.7 + 0.2 / - 0.0 Not Adjustable 3.5 ± 0.2
Downflow 120 0.7 + 0.2 / - 0.0 Not Adjustable 3.5 ± 0.2
Upflow 120 0.9 + 0.2 / - 0.0 Not Adjustable 3.5 ± 0.2
For upflow 120KBTU/hr model, 1st stage is 45%
Manifold pressures apply for Natural Gas applications ONLY
▲
WARNING
!
EXPLOSION HAZARD
REPLACE AND/OR
TIGHTEN ALL PLUGS
REMOVED OR LOOS-
ENED WHEN ADJUST-
ING GAS PRESSURE.
LEAK CHECK THE FIT-
TINGS BEFORE PLAC-
ING INTO REGULAR
SERVICE. FAILURE TO
FOLLOW THIS WARNING
COULD RESULT IN SE-
RIOUS PERSONAL IN-
JURY, PROPERTY DAM-
AGE, OR DEATH
Slope
Gauge
6

UHM-DHM-SF-1H 13
Service Facts
h. Allow 5 minutes to pass before attempting to adjust
the 40% manifold pressure. This will insure that
the learning routine is complete and that the heat
rise is stable.
j. Read the 40% manifold pressure.
k. If needed, remove the low heat manifold adjust-
ment cover and adjust to obtain the correct mani-
fold pressure. See Figure 7.
40% (LOW) HEAT ADJUSTMENT: TURN CLOCK-
WISE TO DECREASE MANIFOLD PRESSURE
OR COUNTERCLOCKWISE TO INCREASE
MANIFOLD PRESSURE.
l. Use Manifold Pressure Settings Table 1 for the
correct manifold pressure setting in Inches of Water
Column.
m. Once the 40% manifold pressure has been adjusted;
push the Enter button on the user interface. This
will stop the gas valve setup mode and take you
back to the home screen.
3) Setting “MAX” manifold gas pressure
To enter the Gas Valve Setup mode:
a. Scroll down on the user interface to Unit Test.
b. Scroll to the right and select “Gas Val Setup”.
c. Push the Enter button.
d. Scroll to the right and select MAX; then push the
Enter button.
e. Select “MAX” and push the Enter button.
f. When asked “Are You Sure”, select Yes, and push
the Enter button.
g. The furnace will now begin another ignition se-
quence.
h. If pressure switch 2 & 3 learning routines have not
been performed; after successful ignition, the
inducer will go through this operation. (see Inducer
Learning Routine section).
i. Allow 5 minutes to pass before attempting to adjust
the 100% manifold pressure. This will insure that
the learning routine is complete and that the heat
rise is stable.
j. Read the 100% manifold pressure.
k. If needed, remove the high heat manifold adjust-
ment cover and adjust to obtain the correct mani-
fold pressure. See Figure 7.
100% (HIGH) HEATADJUSTMENT:
COUNTERCLOCKWISE TO DECREASE MANI-
FOLD PRESSURE OR CLOCKWISE TO IN-
CREASE MANIFOLD PRESSURE.
l. Use Manifold Pressure Settings Table 1 for the
correct manifold pressure setting in Inches of Water
Column.
m. Replace and tighten the adjustment cover for the
high heat and read the manifold pressure again.
This procedure may need to be repeated until the
correct manifold pressure is obtained.
NOTE: The adjustment cover over the high heat must
be in place during manifold gas pressure readings.
See Figure 6.
n. If the firing rate cannot be obtained with the
manifold pressures specified in Table 1, the orifices
must be changed. If a change of orifices is required
to correct the furnace input rating, refer to Table 17
on page 37 of the Installer's guide.
o. Once the 100% manifold pressure has been ad-
justed; push the Enter button on the user interface.
This will stop the gas valve setup mode and take
you back to the home screen.
▲
WARNING
!
EXPLOSION HAZARD
REPLACE AND/OR TIGHTEN ALL PLUGS
REMOVED OR LOOSENED WHEN ADJUST-
ING GAS PRESSURE. LEAK CHECK THE
FITTINGS BEFORE PLACING INTO REGU-
LAR SERVICE.
FAILURE TO FOLLOW THIS WARNING
COULD RESULT IN SERIOUS PERSONAL
INJURY, PROPERTY DAMAGE, OR DEATH.
p. Remove all field supplied tubing and measurement
devices. Reinstall and tighten all covers and outlet
pressure tap screw.
q. Leak test all gas fittings using a leak detection
solution or soap suds.
r. Turn comfort control to home owners desired
temperature.
PERSONALITY MODULE
The Personality Module is a removable memory device,
on which is stored model specific data required for
proper furnace operation. The Personality Module is
tethered to the unit and must remain with the furnace
at all times. The Personality module must remain
plugged into the furnace IFC.

14 UHM-DHM-SF-1H
Service Facts
STAND ALONE OPERATION
(CONTINGENCY MODE)
The Contingency Mode allows the installer to set the
equipment to operate in an ON/ OFF Duty Cycle
mode. This mode will be activated using the User
Interface. Contingency Mode is NOT available in
24VAC mode. The user will select the desired level
of capacity required, Stage 1 (40%) or 2 (100%). The
user will select the desired ON/ OFF Duty Cycle,
10% minimum to 50% maximum, (10% increments,
10% = 2 minutes On, 18 minutes Off; 50% = 10
minutes on, 10 minutes off).
CONTINGENCY MODE
Note:
Stage 1 = 40% (low) heat, Stage 2 = 100% (high) heat
Note:
If a communicating comfort control is detected to be
present and the contingency mode is selected,
NOT AVAILABLE will be displayed on the User
Interface.
•Stand alone operation can only be entered at the
user interface.
• Stand alone operation can be set up to operate the
furnace in Heating Only.
• The contingency mode is used when the communi-
cating comfort Control is not communicating with
the furnace or when setting gas manifold pres-
sures.
• Before attempting to enter contingency mode,
disconnect the Data wire "D" from the Furnace
IFC terminal block.
•The contingency mode will function only when the
Furnace IFC is not flashing a fault code at its
Fault LED.
•To enter the contingency mode of operation, turn
115 VAC power off. When the Green LED on the
variable speed inducer drive goes out, turn 115
VAC power back on.
• Scroll down using the down arrow 6at the User
Interface until you see CNTNGNCY Mode, then
press the Enter button.
•CNTNGNCY MODE and 3STAGE 4will now
be displayed. Press the Enter button.
•STAGE and 3OFF [OFF] will now be displayed.
First or Second heat stage must be selected. Use
the 3or4arrows to select the stage
of heat wanted and then push the Enter button
and then the 6button.
•DUTY CYCLE and 10% [10%] will now be dis-
played. A duty cycle must now be selected from 10
to 50%. A 10% duty cycle will run the furnace for
2 minutes and then off for 18 minutes. A 50%
duty cycle will run the furnace for 10 minutes and
then be off for 10 minutes. These duty cycles
will be repeated 3 times per hour. Use the 3or4
arrows to select a duty cycle and then push the
Enter button and then the 6 button.
•Start and NO [NO] will now be displayed. With
a NO/NO question being asked, use the 3or4
arrows to select the YES and then press the
ENTER button.
•Are you Sure and NO [NO] will now be dis-
played. With a NO/ NO question being asked,
use the 3or4arrows to select the YES and then
press the ENTER button.
•Turn 115VAC power off. When the Green LED on
the variable speed inducer drive goes out, turn
115 VAC power back on.
•When the furnace is operating in the contingency
mode (stand alone operating cycle), the user
interface will display the following information.
The top line will say CNTNGNCY MODE. The
bottom line will show the duty cycle stage num-
ber STG (1 or 2) selected, and the percent num-
ber 10-50 % selected.
•All furnace operating controls, pressure switches
and communications between the IFC and the
variable speed inducer drive and the variable
speed indoor blower will be functional during
contingency mode operation of the furnace.
•The 3456 and ENTER buttons do not func-
tion in the contingency mode of operation.
•To exit the contingency mode of operation turn
off the 115 VAC power to the furnace.
•The contingency mode will stop for any of the
following reasons:
(1) If the furnace IFC receives a signal from
the communicating comfort control. This will
only happen if the data wire "D" from the comfort
control has been reconnected to the furnace IFC
terminal board terminal "D".
(2) Power is removed from the furnace and
then turned back on.
(3) The Furnace IFC enters a RESET mode
of operation.
(4) A fault is detected by the furnace IFC.
Fault LED will be flashing anAlert Code.
24V CONTINGENCY MODE
An alternative method for the contingency mode can
be used by changing the mode of operation in the
Use Interface to 24V mode and installing a
conventional 24V comfort control.
To set this mode of operation:
Remove all wiring from the *CONT900 comfort
control and install a 24V comfort control. If the
comfort control requires a 24V common; connect
R and B to respective terminals. Connect a third
wire to "W". At the control board, connect the
same three wires to the corresponding terminals.
Jumper W1 to W2 at the control board. The
stage delay between W1 and W2 can be set by
scrolling thru the User Interface. It is factory set
to zero minutes but can be adjusted to 5, 10, or
15 minutes.

UHM-DHM-SF-1H 15
Service Facts
IFC INDUCER LEARNING ROUTINE SEQUENCE
Note:
Stage 1 = 40% (low) heat, Stage 2 = 100% (high) heat
•The furnace IFC will go through an inducer learn-
ing routine for three pressure switches.
•The learning routine is done to determine the
correct amount of ventilation air for complete
combustion.
• The inducer motor speed may be different for each
installation due to the different length and size of
the ventilation pipe, exhaust vent pipe, number
of pipe fittings used, and the type of vent cap
installed.
• The inducer learning routine is repeated each time
the power to the furnace is interrupted. Once
power is restored and the furnace receives a call
for heat, the PS-1, PS-2 inducer learning routine
will be initiated. The furnace IFC will not go
through a PS-3 inducer learning routine until it
receives a call for 100% (high) heat.
• To ensure the furnace heating efficiency is main-
tained the furnace IFC will repeat the inducer
motor learning routine after :
150 Cycles at 40% (low) heat
100 Cycles at 65% (medium) heat
50 Cycles at 100% (high) heat
PS-1, PS-2 Inducer Learning Routine
•The furnace IFC checks the pressure switches PS-
1, PS-2 and PS-3. They all have to be open before
a heating cycle can begin.
• The furnace IFC sends a digital signal to the
variable speed inducer drive to run the inducer
motor at the preset factory 65% (medium) heat
RPM.
• The furnace IFC waits for the PS-1 and PS-2
pressure switches to close. A 24 Volt AC signal is
sent to the furnace IFC when a pressure switch
closes.
• If PS-1 and PS-2 do not close at the preset factory
65% (medium) heat RPM, the furnace IFC will
continue to signal the variable speed inducer
drive to increase the inducer speed in steps until
PS-1 and PS-2 close or until the maximum RPM
for 65% (medium) heat is reached.
• When PS-1 and PS-2 switches close, the furnace
IFC will then start the ignition cycle.
• The IFC now starts the igniter warm up cycle.
• Near the end of the warm up cycle the furnace
IFC will turn on the gas valve.
NOTE: The furnace lights at approximately
65% of capacity.
• When the burner flame is detected by the
furnace IFC, a forty-five second time delay
for indoor blower operation begins. The
forty-five second time delay allows the heat
exchanger and the recuperative cell to
warm up.
• The furnace IFC will now start its 65% (me-
dium) heat inducer learning routine.
• The furnace IFC will signal the variable
speed inducer drive beginning to reduce
the inducer motor speed in steps until the
furnace IFC detects that PS-2 is open.
• When PS-2 opens, the furnace IFC will
NOTE the inducer motor RPM.
• The furnace IFC then adds an additional
number of RPM to the 65% (medium) heat
inducer motor NOTED RPM until PS-2
closes.
• The additional number of RPM plus this
NOTED RPM is the learned 65% (medium)
heat inducer operating RPM.
• The furnace IFC now stores this learned op-
erating inducer RPM for 65% (medium)
heat in its memory.
• The furnace IFC will use this stored learned
operating inducer RPM for 65% (medium)
heat calls it receives in the future.
• If the furnace IFC is still receiving a call for
low heat operation it will now start the
learning routine for 40% (low) heat.
• The furnace IFC will then continue to re-
duce the inducer motor RPM in steps until
the furnace IFC detects that PS-1 is open.
• When PS-1 opens, the furnace IFC will
NOTE the inducer motor RPM.
• The furnace IFC then adds an additional
number of RPM to the 40% (low) heat in-
ducer motor NOTED RPM until PS-1
closes.
• The additional number of RPM plus this
NOTED RPM is the learned 40% (low) heat
inducer operating RPM.
• The furnace IFC now stores this learned in-
ducer operating RPM for 40% (low) heat in
its memory.
• The furnace IFC will use this stored learned
inducer operating RPM for 40% (low) heat
calls it receives in the future.
• Whenever the furnace is powered up or af-
ter a RESET, the furnace IFC will not go
through a learning routine for 100% (high)
heat until it receives a call for 100% (high)
heat.

16 UHM-DHM-SF-1H
Service Facts
PERIODIC SERVICING REQUIREMENTS
▲
WARNING
!
Disconnect power to the unit before removing the
Blower door. Allow a minimum of 10 seconds for IFC
power supply to discharge to 0 volts.
Failure to follow this warning could result in property
damage, personal injury or death.
▲
WARNING
!
CARBON MONOXIDE POISONING HAZARD
Failure to follow the service and/ or periodic mainte-
nance instructions for the Furnace and venting system,
could result in carbon monoxide poisoning or death.
1. GENERAL INSPECTION – Examine the furnace
installation annually for the following items:
a. All flue product carrying areas external to the
Furnace (i.e. chimney, vent connector) are clear
and free of obstruction. A vent screen in the end
of the Vent (flue) Pipe must be inspected for
blockage annually.
b. The vent connector is in place, slopes upward
and is physically sound without holes or exces-
sive corrosion.
c. The return air duct connection(s) is physically
sound, is sealed to the Furnace and terminates
outside the space containing the Furnace.
d. The physical support of the Furnace should be
sound without sagging, cracks, gaps, etc., around
the base so as to provide a seal between the sup-
port and the base.
e. There are no obvious signs of deterioration of the
Furnace.
INDOOR BLOWER TIMING
Heating: The Integrated Furnace Control module
controls the Indoor Blower. The Blower
start is fixed at 45 seconds after ignition.
The FAN-OFF period is field selectable
via the User Interface menu at 60, 100,
140, or 180 seconds. The factory setting is
100 seconds.
Cooling: Continuous Fan mode is 50% of the cool-
ing CFM. This is a selectable range on
the Comfort Control menu.
When in communicating mode, see Use Interface Menu
in furnace Installer's Guide.
PS-3 Inducer Learning Routine
Note:
Stage 1 = 40% (low) heat, Stage 2 = 100% (high) heat
• When the furnace IFC receives a digital signal for
100% (high) heat from the comfort control it will
begin the PS-3 inducer learning routine.
• The furnace will start the heating cycle in 65%
(medium) heat, if not already on, and then begins
the PS-3 inducer learning routine.
• The furnace IFC will send a digital signal to the
variable speed inducer drive to run the inducer
motor at the preset factory 100% (high) heat
RPM.
• The furnace IFC waits for PS-3 pressure switch to
close. A 24 Volt AC signal is sent to the furnace
IFC when the pressure switch closes.
• If PS-3 does not close at the factory preset 100%
(high) heat RPM, the furnace IFC will continue to
signal the variable speed inducer drive to in-
crease the inducer speed in steps until PS-3
closes or until the maximum RPM for 100%
(high) heat is reached.
• The furnace IFC enters a time delay so that the
heat exchanger and the recuperative cell warm
up to their high heat operating temperature. At
the end of this time delay, the inducer discharge
air temperature will be at its high heat operating
temperature and the density of the products of
combustion will be stabilized.
• The furnace will now signal the variable speed
inducer drive to reduce the inducer speed in steps
until PS-3 opens.
• When PS-3 opens, the furnace IFC will NOTE the
inducer motor RPM.
• The furnace IFC then adds an additional number
of RPM to the 100% (high) heat inducer motor
NOTED RPM until PS-3 closes.
• The furnace IFC now stores this learned inducer
operating RPM for 100% (high) heat in its
memory.
• The furnace IFC will use this stored learned
inducer operating RPM for 100% (high) heat calls
it receives in the future.
• If PS-3 is not closed when the inducer reaches its
maximum RPM, the furnace IFC will signal the
variable speed inducer drive to reduce the in-
ducer Motor speed in steps to its low heat
LEARNED SPEED.
• The furnace IFC flashes its Red Fault LED three
times repeatedly. The furnace IFC will keep
operating at low heat for 10 minutes and then re-
try the PS-3 learning routine.

UHM-DHM-SF-1H 17
Service Facts
2. FILTERS – Filters should be cleaned or replaced
(with high velocity filters only), monthly and more
frequently during high use times of the year such
as midsummer or midwinter.
3. BLOWERS – The Blower size and speed determine
the air volume delivered by the Furnace. The
Blower motor bearings are factory lubricated and
under normal operating conditions do not require
servicing. Annual cleaning of the Blower wheel and
housing is recommended for maximum air output,
and this must be performed only by a qualified
servicer or service agency.
4. IGNITER – This unit has a special hot surface di-
rect ignition device that automatically lights the
burners. Please note that it is very fragile and
should be handled with care.
▲
CAUTION
!
Do NOT touch igniter. It is extremely hot.
5. BURNER – Gas burners do not normally require
scheduled servicing, however, accumulation of for-
eign material may cause a yellowing flame or de-
layed ignition. Either condition indicates that a ser-
vice call is required. For best operation, burners
must be cleaned annually using brushes and
vacuum cleaner.
Turn off gas and electric power supply. To clean
burners, remove Burner Box cover (6 to 8 screws)
and top burner bracket. Lift burners from orifices.
NOTE:
Be careful NOT to break igniter when removing burn-
ers.
Clean burners with brush and/ or vacuum cleaner.
Reassemble parts by reversal of the above proce-
dure. The Burner Box must be resealed when re-
placing box cover.
NOTE:
Natural gas units should not have any yellow tipped
flames. This condition indicates that a service call is re-
quired. For best operation, burners must be cleaned
annually using brushes and vacuum cleaner.
NOTE:
On LP (propane) units, due to variations in BTU content and
altitude, servicing may be required at shorter intervals.
6. HEAT EXCHANGER/ FLUE PIPE – These items
must be inspected for signs of corrosion, and/ or de-
terioration at the beginning of each heating season
by a qualified service technician and cleaned annu-
ally for best operation. To clean flue gas passages,
follow recommendations below:
a. Turn off gas and electric power supply.
b. Inspect flue pipe exterior for cracks, leaks, holes
or leaky joints. Some discoloration of PVC pipe is
normal.
c. Remove burner compartment door from Fur-
nace.
d. Inspect around insulation covering flue collector
box. Inspect induced draft Blower connections
from recuperative cell and to the flue pipe con-
nection.
e. Remove burners. (See 5. Burner)
f. Use a mirror and flashlight to inspect interior of
Heat Exchanger, be careful not to damage the Ig-
niter, Flame Sensor or other components.
g. If any corrosion is present, the Heat Exchanger
should be cleaned by a qualified service techni-
cian.
h. After inspection is complete replace Burner Box
cover, burners, and Furnace door.
i. Restore gas supply. Check for leaks using a soap
solution. Restore electrical supply. Check unit for
normal operation.
7. COOLING COIL CONDENSATE DRAIN - If a cool-
ing coil is installed with the Furnace, condensate
drains should be checked and cleaned periodically to
assure that condensate can drain freely from coil to
drain. If condensate cannot drain freely water dam-
age could occur. (See Condensate Drain in
Installer’s Guide.)

18 UHM-DHM-SF-1H
Service Facts
*UHM WIRING DIAGRAM
▲CAUTION
!
Label all wires prior to disconnection when servicing con-
trols. Wiring errors can cause improper and dangerous op-
eration. Verify proper operation after servicing.

UHM-DHM-SF-1H 19
Service Facts
*UHM SCHEMATIC DIAGRAM
▲
CAUTION
!
Label all wires prior to disconnection when servicing con-
trols. Wiring errors can cause improper and dangerous op-
eration. Verify proper operation after servicing.

20 UHM-DHM-SF-1H
Service Facts
*DHM WIRING DIAGRAM
▲
CAUTION
!
Label all wires prior to disconnection when servicing con-
trols. Wiring errors can cause improper and dangerous op-
eration. Verify proper operation after servicing.